.\" $OpenBSD: IPAddressRange_new.3,v 1.9 2023/10/03 09:58:06 tb Exp $
.\"
.\" Copyright (c) 2023 Theo Buehler <tb@openbsd.org>
.\"
.\" Permission to use, copy, modify, and distribute this software for any
.\" purpose with or without fee is hereby granted, provided that the above
.\" copyright notice and this permission notice appear in all copies.
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.\" THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
.\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
.\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
.\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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.\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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.Dd $Mdocdate: October 3 2023 $
.Dt IPADDRESSRANGE_NEW 3
.Os
.Sh NAME
.Nm IPAddressRange_new ,
.Nm IPAddressRange_free ,
.Nm d2i_IPAddressRange ,
.Nm i2d_IPAddressRange ,
.Nm IPAddressOrRange_new ,
.Nm IPAddressOrRange_free ,
.Nm d2i_IPAddressOrRange ,
.Nm i2d_IPAddressOrRange ,
.Nm IPAddressChoice_new ,
.Nm IPAddressChoice_free ,
.Nm d2i_IPAddressChoice ,
.Nm i2d_IPAddressChoice ,
.Nm IPAddressFamily_new ,
.Nm IPAddressFamily_free ,
.Nm d2i_IPAddressFamily ,
.Nm i2d_IPAddressFamily
.Nd RFC 3779 IP address prefixes and ranges
.Sh SYNOPSIS
.In openssl/x509v3.h
.Ft "IPAddressRange *"
.Fn IPAddressRange_new void
.Ft void
.Fn IPAddressRange_free "IPAddressRange *range"
.Ft IPAddressRange *
.Fo d2i_IPAddressRange
.Fa "IPAddressRange **range"
.Fa "const unsigned char **der_in"
.Fa "long length"
.Fc
.Ft int
.Fo i2d_IPAddressRange
.Fa "IPAddressRange *range"
.Fa "unsigned char **der_out"
.Fc
.Ft "IPAddressOrRange *"
.Fn IPAddressOrRange_new void
.Ft void
.Fn IPAddressOrRange_free "IPAddressOrRange *aor"
.Ft IPAddressOrRange *
.Fo d2i_IPAddressOrRange
.Fa "IPAddressOrRange **aor"
.Fa "const unsigned char **der_in"
.Fa "long length"
.Fc
.Ft int
.Fo i2d_IPAddressOrRange
.Fa "IPAddressOrRange *aor"
.Fa "unsigned char **der_out"
.Fc
.Ft "IPAddressChoice *"
.Fn IPAddressChoice_new void
.Ft void
.Fn IPAddressChoice_free "IPAddressChoice *ac"
.Ft IPAddressChoice *
.Fo d2i_IPAddressChoice
.Fa "IPAddressChoice **ac"
.Fa "const unsigned char **der_in"
.Fa "long length"
.Fc
.Ft int
.Fo i2d_IPAddressChoice
.Fa "IPAddressChoice *ac"
.Fa "unsigned char **der_out"
.Fc
.Ft "IPAddressFamily *"
.Fn IPAddressFamily_new void
.Ft void
.Fn IPAddressFamily_free "IPAddressFamily *af"
.Ft IPAddressFamily *
.Fo d2i_IPAddressFamily
.Fa "IPAddressFamily **af"
.Fa "const unsigned char **der_in"
.Fa "long length"
.Fc
.Ft int
.Fo i2d_IPAddressFamily
.Fa "IPAddressFamily *af"
.Fa "unsigned char **der_out"
.Fc
.Sh DESCRIPTION
.Vt IPAddressRange ,
.Vt IPAddressOrRange ,
.Vt IPAddressChoice ,
and
.Vt IPAddressFamily
are building blocks of the
.Vt IPAddrBlocks
type representing the RFC 3779 IP address delegation extension.
.Pp
Per RFC 3779, section 2.1.1,
an IPv4 or an IPv6 address is encoded in network byte order in an
ASN.1 BIT STRING of bit size 32 or 128 bits, respectively.
The bit size of a prefix is its prefix length;
all insignificant zero bits are omitted
from the encoding.
Per section 2.1.2,
an address range is expressed as a pair of BIT STRINGs
where all the least significant zero bits of the lower bound
and all the least significant one bits of the upper bound are omitted.
.Pp
The library provides no API for directly converting an IP address or
prefix (in any form) to and from an
.Vt ASN1_BIT_STRING .
It also provides no API for directly handling ranges.
The
.Vt ASN1_BIT_STRING
internals are subtle and directly manipulating them in the
context of the RFC 3779 API is discouraged.
The bit size of an
.Vt ASN1_BIT_STRING
representing an IP address prefix or range is eight times its
.Fa length
member minus the lowest three bits of its
.Fa flags ,
provided the
.Dv ASN1_STRING_FLAG_BITS_LEFT
flag is set.
.Pp
The
.Vt IPAddressRange
type defined in RFC 3779 section 2.2.3.9 is implemented as
.Bd -literal -offset indent
typedef struct IPAddressRange_st {
	ASN1_BIT_STRING *min;
	ASN1_BIT_STRING *max;
} IPAddressRange;
.Ed
.Pp
It represents the closed range [min,max] of IP addresses between
.Fa min
and
.Fa max ,
where
.Fa min
should be strictly smaller than
.Fa max
and the range should not be expressible as a prefix.
.Pp
.Fn IPAddressRange_new
allocates a new
.Vt IPAddressRange
object with allocated, empty
.Fa min
and
.Fa max ,
thus representing the entire address space invalidly as a non-prefix.
.Pp
.Fn IPAddressRange_free
frees
.Fa range
including any data contained in it.
If
.Fa range
is
.Dv NULL ,
no action occurs.
.Pp
There is no dedicated type representing the
.Vt IPAddress
type defined in RFC 3779 section 2.2.3.8.
The API uses
.Vt ASN1_BIT_STRING
for this.
.Pp
The
.Vt IPAddressOrRange
type defined in RFC 3779 section 2.2.3.7 is implemented as
.Bd -literal -offset indent
typedef struct IPAddressOrRange_st {
	int type;
	union {
		ASN1_BIT_STRING *addressPrefix;
		IPAddressRange *addressRange;
	} u;
} IPAddressOrRange;
.Ed
.Pp
representing an individual address prefix or an address range.
The
.Fa type
member should be set to
.Dv IPAddressOrRange_addressPrefix
or
.Dv IPAddressOrRange_addressRange
to indicate which member of the union
.Fa u
is valid.
.Pp
.Fn IPAddressOrRange_new
returns a new
.Vt IPAddressOrRange
object with invalid type and
.Dv NULL
members of the union
.Fa u .
.Pp
.Fn IPAddressOrRange_free
frees
.Fa aor
including any data contained in it,
provided
.Fa type
is set correctly.
If
.Fa aor
is
.Dv NULL ,
no action occurs.
.Pp
In order to express a list of address prefixes and address ranges,
RFC 3779 section 2.2.3.6
uses an ASN.1 SEQUENCE,
which is implemented via a
.Xr STACK_OF 3
construction over
.Vt IPAddressOrRange :
.Bd -literal -offset indent
typedef STACK_OF(IPAddressOrRange) IPAddressOrRanges;
.Ed
.Pp
Since an
.Vt IPAddressOrRanges
object should be sorted in a specific way (see
.Xr X509v3_addr_canonize 3 ) ,
a comparison function is needed for a correct instantiation
with
.Xr sk_new 3 .
The
.Fn v4IPAddressOrRange_cmp
and
.Fn v6IPAddressOrRange_cmp
functions are not directly exposed and not easily accessible
from outside the library,
and they are non-trivial to implement.
It is therefore discouraged to use
.Vt IPAddressOrRanges
objects that are not part of an
.Vt IPAddrBlocks
object.
.Pp
The
.Dq inherit
marker from RFC 3779 section 2.2.3.5 is implemented as
.Vt ASN1_NULL .
It has no dedicated type or API and can be instantiated with
.Xr ASN1_NULL_new 3 .
.Pp
The
.Vt IPAddressChoice
type defined in RFC 3779 section 2.2.3.4 is implemented as
.Bd -literal -offset indent
typedef struct IPAddressChoice_st {
	int type;
	union {
		ASN1_NULL *inherit;
		IPAddressOrRanges *addressesOrRanges;
	} u;
} IPAddressChoice;
.Ed
.Pp
where the
.Fa type
member should be set to
.Dv IPAddressChoice_inherit
or
.Dv IPAddressChoice_addressesOrRanges
to indicate whether a given
.Vt IPAddressChoice
object represents an inherited list or an explicit list.
.Pp
.Fn IPAddressChoice_new
returns a new
.Vt IPAddressChoice
object with invalid type and
.Dv NULL
members of the union
.Fa u .
.Pp
.Fn IPAddressChoice_free
frees
.Fa ac
including any data contained in it,
provided
.Fa type
is set correctly.
.Pp
The
.Fa addressFamily
element defined in RFC 3779 section 2.2.3.3 is implemented as an
.Vt ASN1_OCTET_STRING
and it contains two or three octets.
The first two octets are always present and represent the
address family identifier (AFI)
in network byte order.
The optional subsequent address family identifier (SAFI)
occupies the third octet.
For IPv4 and IPv6,
.Dv IANA_AFI_IPV4
and
.Dv IANA_AFI_IPV6
are predefined.
Other AFIs are not supported by this implementation.
.Pp
The
.Vt IPAddressFamily
type defined in RFC 3779 section 2.2.3.2 is implemented as
.Bd -literal -offset indent
typedef struct IPAddressFamily_st {
	ASN1_OCTET_STRING *addressFamily;
	IPAddressChoice *ipAddressChoice;
} IPAddressFamily;
.Ed
.Pp
The
.Fa addressFamily
member indicates the address family the
.Fa ipAddressChoice
represents.
.Pp
.Fn IPAddressFamily_new
returns a new
.Vt IPAddressFamily
object with empty
.Fa addressFamily
and invalid
.Fa ipAddressChoice
members.
.Pp
.Fn IPAddressFamily_free
frees
.Fa af
including any data contained in it.
If
.Fa af
is
.Dv NULL ,
no action occurs.
.Pp
The
.Vt IPAddrBlocks
type defined in RFC 3779 section 2.2.3.1
uses an ASN.1 SEQUENCE,
which is implemented via a
.Xr STACK_OF 3
construction over
.Vt IPAddressFamily :
.Bd -literal -offset indent
typedef STACK_OF(IPAddressFamily) IPAddrBlocks;
.Ed
.Pp
It can be instantiated with
.Fn sk_IPAddressFamily_new_null
and the correct sorting function can be installed with
.Xr X509v3_addr_canonize 3 .
To populate it, use
.Xr X509v3_addr_add_prefix 3
and related functions.
.Pp
.Fn d2i_IPAddressRange ,
.Fn i2d_IPAddressRange ,
.Fn d2i_IPAddressOrRange ,
.Fn i2d_IPAddressOrRange ,
.Fn d2i_IPAddressChoice ,
.Fn i2d_IPAddressChoice ,
.Fn d2i_IPAddressFamily ,
and
.Fn i2d_IPAddressFamily
decode and encode ASN.1
.Vt IPAddressRange ,
.Vt IPAddressOrRange ,
.Vt IPAddressChoice ,
and
.Vt IPAddressFamily
objects.
For details about the semantics, examples, caveats, and bugs, see
.Xr ASN1_item_d2i 3 .
There is no easy way of ensuring that the encodings generated by
these functions are correct, unless they are applied to objects
that are part of a canonical
.Vt IPAddrBlocks
structure, see
.Xr X509v3_addr_is_canonical 3 .
.Sh RETURN VALUES
.Fn IPAddressRange_new
returns a new
.Vt IPAddressRange
object with allocated, empty members, or
.Dv NULL
if an error occurs.
.Pp
.Fn IPAddressOrRange_new
returns a new, empty
.Vt IPAddressOrRange
object or
.Dv NULL
if an error occurs.
.Pp
.Fn IPAddressChoice_new
returns a new, empty
.Vt IPAddressChoice
object or
.Dv NULL
if an error occurs.
.Pp
.Fn IPAddressFamily_new
returns a new
.Vt IPAddressFamily
object with allocated, empty members, or
.Dv NULL
if an error occurs.
.Pp
The decoding functions
.Fn d2i_IPAddressRange ,
.Fn d2i_IPAddressOrRange ,
.Fn d2i_IPAddressChoice ,
and
.Fn d2i_IPAddressFamily
return an
.Vt IPAddressRange ,
an
.Vt IPAddressOrRange ,
an
.Vt IPAddressChoice ,
or an
.Vt IPAddressFamily
object, respectively,
or
.Dv NULL
if an error occurs.
.Pp
The encoding functions
.Fn i2d_IPAddressRange ,
.Fn i2d_IPAddressOrRange ,
.Fn i2d_IPAddressChoice ,
and
.Fn i2d_IPAddressFamily
return the number of bytes successfully encoded
or a value <= 0 if an error occurs.
.Sh SEE ALSO
.Xr ASIdentifiers_new 3 ,
.Xr ASN1_BIT_STRING_new 3 ,
.Xr ASN1_OCTET_STRING_new 3 ,
.Xr ASN1_OCTET_STRING_set 3 ,
.Xr crypto 3 ,
.Xr X509_new 3 ,
.Xr X509v3_addr_add_inherit 3 ,
.Xr X509v3_addr_inherits 3 ,
.Xr X509v3_addr_subset 3
.Sh STANDARDS
RFC 3779: X.509 Extensions for IP Addresses and AS Identifiers:
.Bl -dash -compact
.It
section 2.1.1: Encoding of an IP Address or Prefix
.It
section 2.1.2: Encoding of a Range of IP Addresses
.It
section 2.2.3: Syntax
.It
section 2.2.3.1: Type IPAddrBlocks
.It
section 2.2.3.2: Type IPAddressFamily
.It
section 2.2.3.3: Element addressFamily
.It
section 2.2.3.4: Element ipAddressChoice and Type IPAddressChoice
.It
section 2.2.3.5: Element inherit
.It
section 2.2.3.6: Element addressesOrRanges
.It
section 2.2.3.7: Type IPAddressOrRange
.It
section 2.2.3.8: Element addressPrefix and Type IPAddress
.It
section 2.2.3.9: Element addressRange and Type IPAddressRange
.El
.Pp
ITU-T Recommendation X.690, also known as ISO/IEC 8825-1:
Information technology - ASN.1 encoding rules:
Specification of Basic Encoding Rules (BER), Canonical Encoding
Rules (CER) and Distinguished Encoding Rules (DER),
section 8.6: Encoding of a bitstring value
.Sh HISTORY
These functions first appeared in OpenSSL 0.9.8e
and have been available since
.Ox 7.1 .
.Sh BUGS
.\" The internals do not seem to consistently apply and check
.\" .Dv ASN1_STRING_FLAG_BITS_LEFT
.\" which may lead to incorrect encoding and misinterpretation
As it stands, the API is barely usable
due to missing convenience accessors, constructors and destructors
and due to the complete absence of API that checks that the
individual building blocks are correct.
Extracting information from a given object can be done relatively
safely.
However, constructing objects is very error prone, be it
by hand or using the bug-ridden
.Xr X509v3_addr_add_inherit 3
API.
.Pp
RFC 3779 has element
.Dq addressesOrRanges .
Its type in this API is
.Vt IPAddressOrRanges .
